Some prior art textile machines include working units which are each provided with a small box, containing empty tubes, from which the tubes are taken out or removed by the operator when full tubes are exchanged for empty ones, and which, after having been emptied, must be replenished.
To provide automation of the tube replenishment operation there have been developed machines including a stationary channel disposed along their working units, in which the tubes, arranged in the form of a column, are displaced from one working unit to the other (see, e.g., U.S. Pat. No. 4,040,573). Since the tube length is typically smaller than the spacing between the working units, it is not possible to locate the tube opposite the working unit, and thus withdrawal of tubes out of the channel cannot be automated without further provisions. In particular, in order to enable continuous operation of a travelling service unit, wherein he service unit exchanges the bobbins successively between one working unit and another, a device has been provided wherein the forward most or leading tube in the column is removed or withdrawn from the channel, and the entire tube column, just prior to this withdrawal, is shifted over a distance equal to a portion of spacing between the two adjoining units so that this leading tube can be accurately disposed opposite the respective working unit. However, this very simple solution of the problem fails in the the case of a so-called selective bobbin exchange, wherein the full bobbin is doffed after a precisely predetermined yarn length has been wound thereon. There is a necessity for such an exchange, due to the fact that statistical occurrences of thread breakages, particularly during long term machine operation, are distributed randomly along the machine. Although devices have been provided to avoid this disadvantage, common drawbacks of such devices include the considerable complexity of the devices, and difficult maintenance problems associated with them, which result in a frequent incidence of operational failures.
Thus, for instance, in the German Published Application DE-OS No. 35 35 354, there is described a stationary channel extending along the machine frame above the working or spinning units. The channel is provided with spaced apart transverse partitions defining a location for the tube for the given working unit. Above the channel, a chain conveyor is arranged which is provided with arms for carrying an empty tube above the tubes in the channel. If, after doffing a full bobbin, a tube has been removed from the channel, the tube carried by the arms of the conveyor is put in the free space in the channel. This solution is relatively complicated and expensive.
In European Patent Specification No. 149,980, there is disclosed a device having a stationary channel with a slot in its bottom, through which carriers of a stepwise movable conveyor pass. The conveyor is provided with a lever for lifting the carriers. After the exchange of a bobbin, the entire column of empty tubes is forwarded from one end of the machine up to the vacant location. Even though the needed tube supply is provided by this device, the device is, due to its relative complexity, considerably expensive.